Texas Instruments TI-89 Tip List page 386

If you later need to edit your equation library, it is easily done in the matrix editor. You can use the [F6]
Util menu to insert and delete rows.
When you start eqlib(), this pop-up menu is shown:
You can press [ESC] at this point to exit the equation library and return to the home screen. If you
press [3] to choose the pendulum equation, the numeric solver is started:
Press [ENTER] to accept this equation, and the numeric solver continues:
Note that the equation variables are displayed. Refer to the complete user's guide to learn how to use
the numeric solver. In general, use [UP] and [DOWN] to choose the known variables and enter their
values, then select the unknown variable and press [F2] Solve, to find the solution. The numeric solver
works more quickly if you edit the bound variable list, and supply an initial guess for the unknown
variable. For example, if you know that the solution is positive and less than 1000, you might set bound
to {0,1000}. If you know that the solution should be about 120, then you would set the unknown
variable to 120 before pressing [F2] to solve for it.
Unfortunately bound cannot be set from TI Basic. If this was possible, we could further automate the
solution process by including a default bound setting in the equation library definition matrix.
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